This invention relates to staplers in general, and more particularly, to staplers for driving staples of different lengths into a workpiece.
With the ever increasing copy rate for reproduction machines such as copier duplicators, the need persists for equipment that can fasten together copy sets consisting of differing numbers of sheets quickly, efficiently and without interruption of the reproduction cycle. Copier/duplicator arrangements are known for producing sets of copies in precollated order, for assembling a set of copies into a stack and for stapling the copy set together into a booklet. The stapler in such case is generally capable of driving a staple of a single size which is used no matter how many sheets there are in a copy set. This limits the usefulness of the copier/duplicator where there is a wide range in the number of sheets in a set of originals to be reproduced. Thus, for example, if the stapler uses a staple which can fasten together 50 or less sheets of 20 lb. paper, sets having more than 50 sheets either cannot be stapled or will be poorly fastened together. Although use of a stapler using a larger staple would increase the number of sheets that could be fastened together, fastening of sets of a few sheets will result in undesirable overlapping of the staple ends.
In order to increase the capability of a stapler to handle sets of a wide range of number sheets without producing poorly fastened sets or heavily overlapped staples, a number of arrangements have been proposed to produce staples having different lengths. In staplers using preformed staples, the entire stapling mechanism must be changed manually to accommodate staples of different lengths. In staplers which form the staples from staple blanks cut from a continuous length of staple material, change of staple length is effected manually by changing one or more of the stapler components such as the staple material feeder, the position of the staple material severing mechanism or replacing the staple forming head. In any case, a manual changeover requires interruption of the stapling process which may result in interruption of the copier/duplicator process when the stapler is operating in synchronism therewith. Thus, copy output and efficiency is decreased and cost is increased.